I want my cars to react realistic on collisions. At the moment I can detect when one of the vertices of a car lies in the other car . But I don't know how to react on this collision . All I do is calculating the cars positions back in time to a moment where they don't overlap.

That's not exactly the thing I was looking for. I already know these formulas. I wanted to create a kind of physics engine, which can calculate the movement of the cars easily by adding a force vector to the cars "force situation"...